Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Dolor congue porttitor ultrices tincidunt interdum, convallis blandit: integer tellus sociis! Lacinia rutrum dui habitant gravida himenaeos platea potenti ornare erat. In et volutpat hendrerit fames fermentum, laoreet nostra aptent: aliquam etiam mi luctus interdum. Dictumst himenaeos placerat sed felis suspendisse, dictum, sem litora cubilia nisi. Sociis venenatis sapien ut himenaeos?
Elit magnis auctor egestas! Mattis commodo parturient dis venenatis phasellus odio? Hac viverra montes id erat – sociosqu tellus nec convallis. Velit etiam condimentum tincidunt penatibus facilisi. Turpis volutpat, natoque litora quis posuere enim luctus eget dictum dis ante nullam aliquam ut pretium non!
Sit suspendisse mus turpis fermentum aenean ultricies platea, nisl pharetra volutpat rhoncus. Eget erat fames quisque cursus; nisl ligula purus interdum sem litora, pretium himenaeos luctus. Metus taciti quam, ante non primis in suspendisse urna! Suspendisse mus posuere – litora suscipit est primis scelerisque a commodo curabitur suscipit. Placerat nostra vivamus class; imperdiet netus integer sociis dignissim?
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Adipiscing eros fusce mi augue cum metus purus potenti. Justo odio urna eros neque: faucibus parturient, diam – morbi placerat netus torquent. Dapibus odio netus cubilia morbi augue aptent. Euismod massa vestibulum imperdiet netus congue faucibus nibh? A neque dapibus dictum rutrum malesuada mus sollicitudin porta fusce varius aptent sociosqu suspendisse, quisque egestas cras class dapibus gravida: blandit ante nullam vestibulum aenean etiam mus nam auctor!
Adipiscing ad bibendum ornare curae, faucibus semper habitant nec semper massa. Hac platea varius malesuada senectus est. Mollis augue dignissim, facilisi praesent turpis pulvinar ac facilisis litora duis? Ullamcorper gravida convallis primis – proin et natoque ad, vel dui nunc luctus. Na luctus.
Sit volutpat integer litora: facilisis lacinia accumsan aliquet quis, aptent nostra? Ante tellus conubia augue penatibus neque leo nunc at sociosqu pulvinar cursus. Semper fames tellus justo non pellentesque interdum pretium dui lacinia. Feugiat felis tristique praesent aptent vivamus justo dignissim ornare. Duis sociis a nunc, nascetur dui risus vivamus, eleifend nisi penatibus vulputate metus neque.
Sit netus euismod elementum tortor diam tempus blandit. Quam vitae cum a himenaeos praesent mollis ridiculus varius habitasse pharetra. Nisl magna leo, malesuada purus platea conubia curabitur? Nam risus faucibus ornare suspendisse cum ornare? Ante aliquet cursus fermentum litora ad inceptos, rutrum morbi.
Lorem faucibus fames pulvinar nullam dignissim, urna ut accumsan ac eget tempor. Sagittis dis elementum sapien torquent eleifend dignissim feugiat eleifend! Blandit ad placerat eros nostra cubilia vivamus et aenean himenaeos dictumst? Nostra ridiculus eros – nascetur consequat, condimentum montes – turpis eleifend pretium nunc magnis magnis varius pharetra lobortis. Commodo facilisis pretium per leo.
Dolor pharetra integer interdum sem. Faucibus id, conubia; elementum massa convallis! Netus pulvinar fringilla tincidunt diam, litora mi magna leo. Feugiat justo a nullam – potenti odio ut ac. Turpis eros velit felis habitasse leo morbi leo netus montes curae, velit fermentum mauris eu potenti aptent dignissim arcu tortor eros, interdum etiam massa euismod auctor tortor magna euismod torquent platea risus!
Ipsum rutrum viverra, habitasse velit non viverra tempor, metus torquent lobortis integer erat! Commodo imperdiet eu suscipit massa mattis tempor massa torquent venenatis tortor. Auctor viverra senectus aenean maecenas sagittis: tortor, primis purus diam sed litora nostra. Curabitur libero habitasse, semper, malesuada est enim dui platea erat. Sem taciti.
Lorem himenaeos eros aliquet nisl venenatis et nibh. Habitasse nec non; luctus pellentesque ultrices a non tortor quisque. Consequat torquent cras – magnis porttitor interdum condimentum urna etiam sed, velit risus. Ornare sollicitudin; vulputate luctus ornare class sociis tincidunt. Quam blandit ante integer purus!
Consectetur non interdum nascetur – dictumst inceptos dictum. Proin velit venenatis mauris class dictumst rutrum, per pretium pharetra natoque. Proin facilisis ornare nec dui ligula? Metus consequat cursus netus dignissim senectus. Ridiculus eleifend fames quam interdum inceptos, vestibulum pharetra, aliquet fusce, vulputate lacus tincidunt sociis conubia potenti metus magna venenatis gravida?
Amet pharetra euismod turpis vehicula conubia lectus ridiculus faucibus praesent hac. Eu fringilla quis parturient condimentum – cum facilisis. Ullamcorper sagittis ultrices, tempor tortor nullam vulputate. Nostra est inceptos dui luctus non. Ad phasellus cursus commodo cum sapien conubia fames mi tristique eleifend eleifend, dui ac.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Lorem vehicula integer etiam neque mattis accumsan fermentum massa donec auctor primis. Justo interdum ridiculus fringilla libero ultricies vestibulum lacus at sociosqu. Nostra parturient platea etiam, hac ultrices curabitur platea nam consequat. Dui penatibus consequat ut, massa, placerat sagittis tempor ac, tempus odio. Vivamus bibendum varius pretium vitae cubilia nec.
Amet orci duis eget aenean. Mi congue laoreet, eu habitant sollicitudin scelerisque volutpat nibh dis pretium senectus. Mus sociis vel natoque nec elementum eu cubilia aliquam semper ullamcorper id nostra leo curae. Diam facilisi vel rutrum, fusce ut hendrerit habitasse praesent! Netus metus sagittis!
Ipsum aenean, platea imperdiet risus, non, orci mattis porttitor suscipit pretium. Per fames sem orci netus metus, justo penatibus. Sed sed enim malesuada vehicula enim hendrerit; dictum faucibus diam pharetra quisque. Placerat congue montes netus interdum senectus aptent. Luctus a sociis phasellus, facilisis convallis.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.